Dehydration takes a major toll on the body. It can make you feel dizzy, tired, and weak. Severe cases can result in vomiting, diarrhea, or fainting. Workers doing physical tasks in hot environments have to be constantly on guard against progressive dehydration.
Sweating is how your body regualtes its temperature when it gets too hot. By wetting the skin and cooling the body’s core temperature when it evaporates, sweat helps the body stay at an optimal temperature.
It’s a necessary function, but it comes with a cost. Sweat contains anywhere from 0.2%–1% solute, meaning that you lose some minerals such as sodium and potassium when you sweat. Very sweaty work result in your body losing up to two liters of water per hour, along with the dissolved solutes, so the effort to replace the depleted substances has to be significant.
Replenishing Electrolytes
Some of the solutes you sweat out are electrolytes. That's a word that's been used a lot in marketing and advertising. But even though a most of us could point out which drinks in the cooler contain them, fewer of us could actually describe what they are or what they do.
Simply put, they are soluble substances that produce an electrically conductive solution when mixed with water (“pure” water is actually not electrically conductive). Some electrolytes, such as sodium and potassium, provide the mechanism by which the muscles, brain, and nervous system function. That's why symptoms like muscle cramps arise when things are out of balance.
When too many electrolytes are lost, you need to rebalance them by introducing more. In this case, by drinking beverages that contain them.
(Learn more about Electrolytes: What They Are and Why They Matter for On-the-Job Hydration
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Why You Might Need Electrolyte Drinks
Under normal circumstances, water loss by sweating and urination can be managed by drinking water.
However, in cases of extreme sweating from heat or exertion, you will also lose a significant amount of electrolytes. In those situations, replacing water alone can lead to hyponatremia or hypokalemia – low sodium or potassium concentration in the blood, respectively.
(Learn more in A Sweaty Situation: PPE, Hydration, and How to Manage Both)
Basically, the concentration of these electrolytes becomes diluted by the excessive introduction of water to a depleted balance of the solute. An electrolyte drink can supplement the balance to account for some of those solute losses.
That doesn't mean that electrolyte drinks are a better choice in all circumstances. Overdoing the electrolyte drinks when you don't need them can overload your system with too many electrolytes, putting your kidneys to work removing the excess. In extreme cases, over-consuming can even lead to the opposite conditions, hyperkalemia (too much potassium) or hypernatremia (too much sodium), each with their own host of undesirable symptoms.
In short, context and quantity are what matter. electrolyte drinks can be a useful supplement when excess sweating is an issue. But they should be consumed with moderation in mind.